The present invention relates to a vehicle drivetrain control system.
With an intention to accelerate a vehicle, the vehicle operator manipulates an accelerator, such as a gas pedal. In this case, if a drive wheel contacts low xcexc(mu) surface and slips, the vehicle fails to speed up as quickly as expected. Slippage of the drive wheel can be suppressed by altering drive torque at the drive wheel. In an attempt to alter drive torque, the drive wheels can be braked and/or environment in which an engine operates can be modified in such a direction as to cause the engine to alter the engine torque.
Usually, the environment surrounding the engine is modified to suppress slippage of the drive wheel. In co-pending U.S. patent application Ser. No. 08/567,590 filed on Dec. 5, 1995, applicants have proposed to close, upon occurrence of slippage of drive wheel, a normally open throttle disposed upstream or downstream of a normally closed throttle, which opens in degrees in response to manipulation of an accelerator. The normally open throttle is closed in response to an engine torque modifier signal developed by a controller. The normally open throttle is adjusted to a desired opening degree including a feedforward term that is determined in the controller as a function of a longitudinal acceleration to which the vehicle is subject to during occurrence of slippage of drive wheel. With the position of the accelerator unchanged, longitudinal acceleration to which the vehicle is subject to varies with varying xcexc(mu) of road surface if the road surface is flat and the vehicle moves in a straight direction. According to this proposal, since, with the same xcexc(mu) surface, the same feedforward term is set over varying road condition, the feedforward term appropriate for driving on flat road surface would cause a reduction of engine torque than necesssary and inappropriate for driving on ascending road.
An object of the invention is to provide a vehicle drivetrain control system, that allows the vehicle to pass through road with varying xcexc(mu) surface under varying drive condition with less alteration in mobility.
According to the invention, there is provided a vehicle drivetrain control system including an engine operable in response to operator manipulation of an accelerator to output varying engine torque, an engine torque modifier operable in response to an engine torque modifier signal for modifying environment in which the engine operates in such a direction as to cause a change in engine torque output by the engine, and a controller means for developing the engine torque modifier signal for operating the engine torque modifier in response to slippage of drive wheel of the vehicle, wherein the controller means determines resistance to which the vehicle moves, and the controller means develops the engine torque modifier signal in response to the determined resistance.